Switch



A. E. BAAK June 26, 1951 SWITCH 3 Sheets-Sheet 1 Filed July 11, 1942 LVVENTOR. Ailoeri" 'E. BaalL.

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Aifoz'ney June 26, 1951 A. E. BAAK 2,557,929

SWITCH Filed July 11, 1942 3 Sheets-Sheet 2 J A M Affornef Patented June 26, 1951 SWKTCH Albert E. Baak, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 11, 1942, Serial N 0. 450,571

13 Claims. 1

This invention relates to new, novel and compact switching devices of light weight and sturdy construction that are adaptable for a wide variety of uses while being capable of withstanding the eiiects of rough treatment and vibration. In particular, the invention relates to unitary switching devices, embodying an electromagnet, for the operation of aircraft warning andcontrol apparatus, although the devices may be employed for the operation of various devices including valves.

A general object of the invention is the provision of a self-contained unitary structure in which a condition responsive means is adjustable for operation over a selected range of condition values and is employed to control a magnetic means for the operation of a switch device that is capable of handling relatively high power and load requirements. The magnetic means of the unitary structure is also adjustably associated with the adjustable condition responsive means to determine the particular values of the condition within the selected range at which the magnetic means is actuated by the condition responsive means.

One object of the invention is the provision of a sturdy, compact and unitary structure in which a main switching device is operated by an electromagnet that is regulated b novel switching means under the control of a condition responsive means, although in a modification of my invention the switching means is manually operable.

A further object of the invention is the provision of a unitary structure having two or more sections. A first section of the structure includes a casing and assembly supporting means, a device to be actuated, an electromagnet for operating the device, and switching mechanism that is magnetically movable and selectively adjustable for controlling the electromagnet. A second section includes one of a plurality of interchangeable base and supporting structures upon which may be mounted a switch actuating means including a condition responsive device, of which varying types and ranges of operation are known. The two sections are associated by mounting means to form a single unit, and adjustable means operated by the condition responsive means is provided for varying the operating range at which the particular condition responsive device actuates the electromagnetic controlled switching mechanism.

An alternate first section may be used interchangeably with that described above where the device to be actuated does not require the speed and power in operation that is provided by the electromagnet, The alternate first section includes a casing and assembly supporting means together with the device to be actuated which may consist of an adjustabl switching mechamsm.

A detailed object of my invention is the production of a switching mechanism that is controlled by one or more pressure responsive members. The pressure responsive members are employed to control the switching mechanism in response to either direct fluid pressures, or to a difference in fluid pressures to which a plurality of bellows members are subjected, or an evacuated bellows may be used that is particularly responsive to ambient pressures. The switching mechanism is also magnetically actuated through armature means operated b an electromagnet and controlled by an auxiliary switch. The auxiliary switch is also magnetically movable by an armature means to provide a mechanical holding circuit for the switch contacts in controlling the relative positioning of the switch contacts and in addition the armature means is selectively adjustable to vary the point at which the switch contacts initially close. To actuate the auxiliary switch an adjustable means is provided that is controlled by the bellows and this means may be adjusted for varying the range of condition values at which the bellows Will operate for energizing and deenergizing the electromagnet. The switching mechanism of my invention is accordingly adapted for use as pressure and differential pressure responsive devices which may, for example, be employed as fuel and oil pressure responsive devices, or as barometric pressure and altitude responsive devices. The switches may accordingly be employed with aircraft that are equipped with superchargers for maintaining a constant fluid pressure for reference purposes in the operation of the switches and also with aircraft that are not so equipped.

Other objects and advantgaes of my invention will become apparent from the following detailed description of the illustrated examples disclosed in the drawings and from a consideration of the appended claims.

Figure 1 is an elevation of any difierential pressure switch unit taken along the lines ll of Figure 2;

Figure 2 is an elevation partly in section of the differential pressure switch unit taken along the lines 22 of Figure 1;

Figure 3 is an elevation of the switch unit taken along the lines 3-3 of Figure 1;

Figure 4 is an elevation, partly in section, of a modification of the switch unit illustrated in Fi ures 1 to 3;

Figure 5 is an elevation, partly in section, of a second modification of the switch illustrated in Figures 1 to 3;

Figure 6 is a view of the casing window and scale employed with my altitude warning switch illustrated in Figure 5; and

Figure 7 is a schematic diagram of a circuit employed with the switch devices illustrated in Figures 1 to 5.

In Figures 1 to 3 of the drawing I have illustrated my differential pressure electromagnetic actuated switch unit which is particularly adapted for use as an aircraft pressure warning switch, although from the following specification it will be apparent that the unit is adaptable for a wide range of uses. The differential pressure warning switch illustrated in Figures 1 to 3 is described in connection with its use as an aircraft gasoline or oil pressure Warning device of the type disclosed in my copending application entitled Switches, Serial No. 437,863, filed April 6, 1942, now Patent No. 2,371,669, and assigned to the asignee of the present application.

The switch is actuated upon the occurrence of a selected drop in differential pressure between the air pressure in a line that is maintained by a supercharger at a given value regardless of aircraft altitudes and the pressure of the fluid fuel for the operation of a Warning device or of a fuel controlling device. In Figures 1 to 3 of the drawings a combination switch base and mounting member In is provided with a plurality of threaded mounting posts and nut members II and I2, respectively, which serve as convenient means for mounting the switch in a desired position and preferably upon a fire wall in close association with the engine. The base I0 is cupshaped and in the bottom portion contains a flanged sleeve member l4 having a threaded passageway formed therein which communicates with the interior of a bellows l6 that is supported upon the sleeve member. The base also contains a flanged sleeve member IB having a threaded passageway i9 formed therein for communication with the interior of a bellows 20. The threaded passageway l5 of bellows I6 is designed to be readily associated with the gasoline fuel line and the passageway I9 directed to the interior of bellows is designed to be readily associated with an airline that is associated with the aircraft engine supercharger. The supercharger maintains the air pressure in the bellows 20 at a substantially constant value regardless of the varying aircraft altitudes.

The fuel pressure actuated bellows i6 has mounted thereon a plunger member 22 and the air pressure actuated bellows 26 has mounted thereon a plunger member 23. A diaphragm 26 is supported between the upper portion of the base member ID and a diaphragm disc supporting member 25 and is also secured to the plunger members 22 and 23 to provide a means for sealing off the interior of the base member to prevent inflammable fuel from reaching the area of the switch contacts in the event of leakage of the bellows IS. A passageway 26 is formed in the side of the cup-shaped base member 40 to provide a vent for the interior of the cup-shaped base member it]. This passageway may readily be connected to a line extending to the exterior of the aircraft for disposing of any fluid whichmay escape within the interior of the base member and also for insuring that each of the bellows is externally acted upon by uniform ambient air pressures.

Mounted upon the diaphragm supporting disc 25 is a gasket member 28 that cooperates with a switch case member 29 for minimizing the effects of vibration to which the switch may be subjected and also for sealing the casing. A switch subassembly base plate 32 is supported by four mounting post members 33. In Figure 2, two of the mounting posts 33 are illustrated and in Figure 3 the remaining two posts 33 are illustrated. As shown, these mounting post members are broken away at one end closely adjacent to the base member In and at the other end closely adjacent to the sub-assembly base plate 32. These posts at one end are secured to the base member ill. The ends of each of the mounting posts upon which are supported the sub-assembly base plate 32 are tapped and threaded to provide passageways which cooperate with similar passageways formed in the sub-assembly base plate 32. Spacing members 35 have threaded end extension portions and the extension on one end cooperates with the threaded passageways of the subassembly plate and the mounting posts 33 for securing the plate to the mounting posts 33. The spacing members 35 have openings 3'! drilled therein to provide convenient means for threadedly securing the spacing members to the plate 32 and supporting members 33. Similar spacing members are provided for each of the four mounting posts. A combination cover and switch assembly supporting member 40 is mounted upon the spacing members. This cover member has apertures formed therein for extension of the upper threaded end portions Al and 42 of the spacing members. A gasket 43 is provided as a seal for the casing 29 and cover 40. Mounted upon the upper threaded end portions All and 42 of each of the spacing members 35 is a nut member 45 and a locking nut 45 for securing the switch cover member 40 to the casing member 29.

An exteriorly threaded sleeve electrical connector plug member is mounted in the cover member 40 and houses therein the electrical connector elements 5| and 52. The connector elements 5| and 52 are supported by an insulating plate member 53 which forms a part of the cover mem ber. The lower end of the connector element 5| is connected to a conducting bracket member 54 and the lower end of the connector element 52 is connected to a conducting bracket member 55. An insulating plate member 51 is supported upon the sub-assembly base member 32 and upon this plate member is mounted a plug member 58 of in sulating material beneath which is arranged the electromagnetic actuated main switch contacts. The main switch contacts consist of two spaced and insulated stationary contacts 60 and 6! and the movable contacts 62 and 63 which are connected by a bridge conducting member 64. The conducting bracket member 54 is connected to the stationary switch contact 60 and the conducting bracket member is connected to the contact 6| as best illustrated in Figure 2 of the drawing. An electromagnet structure referred to generally by the reference character 66 is supported by the sub-assembly base plate 32. An induction coil 61 is supported upon a magnetically conducting coil sleeve member 68 and is separated from the base plate 32 by an insulating sleeve member 69. A first armature member 10 is centrally disposed within the coil sleeve member 68. An armature stop and base member II is connected to sleeve 88 and a plunger member I2 is supported by the stop H. An armature biasing spring I3 is supported upon the plunger member I2 and serves to strongly bias the armature 10 upwardly to a contact open position. A stem member I5 centrally disposed within the armature and supported thereby serves to support the conducting bridge member 64 for operation of the movable switch contacts 62 and G3. The contact carrying bridge member 64 is secured to the stem between two insulating washer members 11 and I8 by a clip member" which is secured to the end of the stem I5.

The induction coil 61 is connected by a conductor 80, as illustrated in Figure 2. to the bracket 55 that is connected to the connector element 52 and also to the stationary main switch contact 8|. A second terminal of the coil is connected by a conductor 8| as illustrated in Figure l, to an auxiliary switch which controls the operation of the electromagnet. The conductor 9I is connected to a fiat spring blade member 82 which carries one contact 83 of the auxiliary switch and the second contact 84 of the auxiliary switch is mounted upon a second magnetically conducting armature member 85, which in conjunction with other parts forms a U shaped assembly.

'The resilient blade or spring member 82 is supported between the insulating sleeve members 81 and 88 which in turn are secured to a threaded bolt member 89. The bolt member is suspended from the horizontal upper portion of an angularly shaped magnetically conducting plate member 90 that is secured to the stop II. A pair of pivot posts 95 and 96 are supported and suspended from the under surface of the sub-assembly mounting plate 32. The horizontal portion of the angular plate 90 has ear portions 9| formed thereon and these ear members are supported in grooves formed in the posts 95 and 96. The downwardly extending portions 92 and 93 Of the plate 90, as illustrated in Figures 1 and 2, provide a magnetic flux path and serve as a pivotal supporting member for the armature 85. The two end portions of the armature member are supported by spring members 91 which are in turn mounted on the under surface of the sub-assembly base plate 32, as illustrated in Figure 2 of the drawing. One end portion of the armature member has formed thereon an outwardly extending projection 99. A magnetically conducting plate member IOI having a tongue member I02 projecting therefrom is secured to the underportion of the magnetically conducting sub-assembly base plate member 32, as illustrated in Figures 1 and 3. A pair of grooves I03 shown in Figure 3 are formed in the tongue I02 for a, purpose to be described below.

An angular plate member I04 has a vertically extending portion with a slot I05 formed therein through which the tongue I02 of plate member Il extends. The tongue I02 serves as a guide for the vertical movement of the angular plate I04 as hereinafter described. The projection 99 of the auxiliary relay armature 85 is also movable within the slot I and the lower slot terminating portion I06 of the plate I04 operates as a stop member for determining the position of the armature 85 and the switch contact 84 carried thereby when the electromagnet is deenergized. The horizontal portion I08 of the angular plate I04 is threadedly supported on the adjustment post I09 to provide for the selective vertical positioning of the armature stop portion I06. The

v adjustment of this member determines the distance between contacts 83, I4, and thus the pressure differential necessary to close the auxiliary switch. The threaded adjustment post I09 extends .through the casing cover member 40, the sub-assembly base plate 32 and the horizontal portion I08 of the angular plate I04 and thus provides for efiecting the adjustment of stop member I00 from the exterior of the casing.

A spring III is mounted between the flange member II2 of the adjustment post I09 and a spring seat plate H3 which the spring forces firmly against the cover member 40. A second spring H5 is mounted upon the adjustment post I09 between the horizontal upper portion I08 of the angular plate I04 and the horizontally extending portion of the plate member IOI. The spring members exert a considerable frictional force on the adjustment post I09 and operate to prevent any undesired movement of the post and associated parts which might otherwise occur, for example, as a result of vibration. The adjustment post I09 has a hex shaped passageway IIB formed axially in the upper end thereof. This passageway is designed to cooperate with a key member to provide for the rotational movement of the threaded adjustment post to selectively determine the vertical positioning of the plate I04 and the armature stop member I05 formed therein. The adjustment post may be rotated by the key to vary the length of the air gap between the armature and the mag netically conducting member IOI when the relay is deenergized. The gap may be varied within a wide operating range of adjustments that is limited only by the ability of the electromagnet to actuate the armature and the ability of contact 83 to engage contact 84.

A cross shaped non-magnetic lever member III has one arm II8 with a U-shaped end portion and the ends of this arm of the lever are movable in the grooves I03 formed on the tongue I02 of member IOI as illustrated in Figure 3. The tongue I02 accordingly serves to guide'and limit the movement of arm II8 of the lever III. The lower ends of the posts and 96 are of conical shape and cooperate with craters I22 and I23 formed in the arm portions I24 and I25, respectively, of the cross shaped lever member III to serve as substantially friction-free pivot members for the lever, as illustrated in Figure 3. The end of the fourth arm I26 of the cross shaped lever member III is secured to a main adjusting spring I28. This main adjusting spring is secured at its other end to a segmental shaped plate member I29 that is mounted upon the threaded adjustment post I 30 and is prevented from being rotated about the post I30 by abutment with the case member. The post I30 has a kerf I34 in the upper end thereof and provides means for the rotation of the threaded post member from the exterior of the casing for varing the vertical positioning of the plate member I29 to correspondingly adjust the force exerted by the main adjusting spring I28. A spring I 3| mounted on the post I30 between the flange I32 and a spring seat plate member I33 operates to frictionally maintain the post I30 in a selected position of adjustment. The main adjusting spring I28 serves to bias arm I26 of the lever III in an upward direction. The lever member I II also has formed therein the crater portions I35 and I36. These crater portions cooperate with the conical shaped heads of the bellows actuated plunger members 23 and 22, respectively, and the bellows plunger members serve as substantially friction-free lever supporting and actuating members. A resilient metallic strip I38 is riveted at one end to the lever member I I1 and the position of the free end of this member may be varied by the screw member I39. An insulating pin I40 is mounted at one end upon the resilient spring member I38. The other end of the insulating pin Mil is inserted in the resilient switch contact carrying arm 82 and the contact carrying end of the arm is supported for movement by the pin. The pin I40 controls the positioning of the switch contact 83 in accordance with the movement of the cross shaped lever I II in response to the difference in pressure exerted thereon by the bellows members I6 and 20. By varying the adjustment of the main spring I28 it is apparent that the pressure required to be exerted by one bellows for movement of the pivoted lever in is increased and that required to be exerted by the other bellows is correspondingly decreased to thus vary the diiferential in pressure required for operation of auxiliary switch actuating lever member ill. The adjustment provided by the main spring I28 is operative to selectively vary the differential pressure between the two bellows required to actuate the auxiliary switch contacts throughout a wide range.

The adjus ment provided by the selectively positioned armature stop member I96 provides for determining the distance the switch actuating lever member Iii must be moved to close switch contacts 83 and 84 for completing a circuit to energize the electromagnet.

Operation difierential pressure will maintain the lever II? The main spring I28 is adjusted to coact with the stop member I06 of plate I06 and in balance.

with bellows 2! so that upon a decrease in pressure of bellows I6 spring nae will cause a definite tipping of lever member I I! in the manner shown in Figure l of the drawing. When the lever is tipped as shown in Figure 1, indicating a decrease in fuel pressure, resilient spring 82 is moved downwardly for a distance which is adjustably controlled by stop I06 to bring contact 83 into engagement with contact 84. The engagement of contact 83, 8'3 closes a circuit for the energization of the induction coil 67 which circuit is shown in Figure '7 and may be traced as follows: from a battery i5il having a ground connection I5 I, current flows through conductor I53, connector 52, tracket 55, conductor 80, induction coil 6?, conductor 8|, switch blade 82, contacts 83, 34, and armature 85, after which it is grounded'to the casing 29. Energization of the induction coil 61 will cau e the armature III to be drawn downwardly within the sleeve 68 and against the bias of spring I3. The downward movement of armature I0 causes a closure of the main switching element, carried by the bridge 64, into engagement with the stationary contacts 80. 6 I. Closure of the main switching element establishes a circuit for the operation of the warning or control device mentioned heretofore, which circuit may be traced as follows: from battery I50, wire I53, connector 52, bracket 55, stationary contact 8|, movable contact 63, bridge 64, movable contact 62, stationary contact 60, bracket 54, connector 5|, wire I54, the load, and wire I55, to ground. Upon energization of the induction coil 61, in addition to causing movement of armature Ill, a magnetic circuit is established to attract arma ture and thus provide a mechanical holding means for the contacts 83, 84, which will increase the pressure between these contacts and thus prevent their accidental opening which may result from vibration of the aircraft. This magnetic circuit includes the coil spool 68, armature i0, sub-assembly base plate 32, angular plate member IGI, angular plate 90, and the armature 85. The extent of the holding action provided by armature 85 with plate I05 aided by springs 91 determines the amount of force which must be exerted by bellows it when the fuel condition is restored to normal, to cause contacts 83, 84 to be opened. When the fuel pressure within bellows It returns to normal the added force provided by bellows 2t and spring I23 will be compensated and lever Ill will return to its horizontal position. When lever H1 is rotated to its horizontal position a movement will be transmitted by spring I38 and pin I46 to spring 82 to cause a separation of contacts 83, a l. When the contacts 83, 8% are opened, the first energizing circuit described heretofore is broken and the armature biasing spring I3 expands to force the armature Ill upward and thus disengage the main switching mechanism controlled by bridge 64. The selective positioning of stop 106 by post I89 regulates the distance between contacts 83, as and thus the distance which one must be moved to engage the other. With the stop we in its lowermost position the pressure differential necessary to close the contacts is increased, while if the stop I536 is moved to its uppermost position, the pressure required to close the contacts is correspondingly decreased. Therefore, the selective positioning of member Hi6 regulates the pressure difierential necessary to close contacts 83, 86 and the adjustment of spring i28 will determine the pressure difierential between the bellows and thus the pressure necessary to actuate the auxiliary switch.

It is frequently desired to operate a signal or other device when the electromagnet of the switch control unit is deenergized. For example,

connector plug member 50. The connector element I58 is connected by a conductor I60 to a stationary switch contact IISI and the connector element I59 is connected by a conductor I62 to a stationary switch contact I63. The switch contact bridging member 64 is actuated as described heretofore by the armature and biasing spring to close the contacts I6I and I63 with the bridging member when the electromagnet is deenergized to establish the following circuit: the grounded battery connection II, battery I50, wire I65, switch connectpr I58, conductor I60, switch contact I6I, bridge v 64, switch contact I63, conductor I62, switch connector I58, wire I66, signal, or other circuit load, I61, and the grounded wire I68.

The distinct operating advantages derived from the provision of the automatic means for the control of the switch unit of my invention may, if desired, be omitted and it is accordingly contemplated that in a modified form the switch of my invention may be manually actuated. For this purpose the cooperative automatic switch actuating structure including the main adjusting spring, the condition responsive means, and the lever actuated thereby, are omitted. In this form of the invention the switch actuating pin I40, as illustrated in Figure 7, is extended through the switch casing or base member and a button formed on the end of the pin extending beyond the casing, not shown, is reciprocated for the manual control of the switch unit.

The modification of my switch unit illustrated in Figure 4 of the drawings relates to a pressure responsive Bourdon tube reverse acting switch. The switch is responsive to the pressure exerted by a fluid in a single line as compared with the differential pressure switch described above. In this embodiment of my invention the Bourdon tube pressure responsive element I10 is supported in a pressure fitting "I that extends through and forms a part of the base member I13. The pressure fitting "I has an internally threaded portion I12 that extends beyond the base I13 to provide meansfor connecting the Bourdon tube with the line containing the fluid of variable pressure employed to actuate the switch. It will be noted that the Bourdon tube may be actuated by the fuel, oil or other fluid line and is operative throughout a range of pressures that is higher than that which may be employed by a bellows of the type illustrated in Figure 1 of the drawing. The base member also has secured thereto a pair of threaded switch mounting post members and one of these members I11 upon which is threaded the nut member I18 is illustrated. These mounting post members correspond to the mounting posts II of the switch unit illustrated in Figures 1 and 3 of the drawings. In Figure 4, two of four switch base mounting posts I80 and I8I are illustrated. These members are i lustrated as being broken at one end closely adjacent to the base member I13 and each member is secured in the base I13. The mounting post members I80 and I8I correspond to the mounting post members 33 and 34 of the switching unit illustrated in Figures 2 and 3 of the drawings. Mounted uponthe end of the Bourdon tube I 10 is a bracket member I85 which has a threaded passageway formed therein. A bolt member I86 is threadedly mounted in the passageway formed in the bracket member I 85 and an insulating switch actuating pin member I81 corresponding to pin I40 is secured to the end of the bolt member I86. An angular bracket member I80 is secured to the base member I13 and the upper horizontally extending portion of this bracket has a slot formed therein which serves as a guide and stop member for the bolt I86 and switch actuating pin I81. It will be apparent that the four mounting posts are designed to be secured to and support thereon the switch sub-assembly base plate member that corresponds to the plate 32 illustrated in Figures 1, 2 and 3 of the drawings.

The base member I13, Bourdon tube I10. bracket I and the switch actuating pin I81 together with the tour switch base mounting posts described above form a unitary structure. The relay, the main and auxiliary switch, the relay core and the associated armatures illustrated diagrammatically in Figure 7 and :which are assembled on the switch sub-assembly base plate 32 and cover member 40 as illustrated in Figures 1 to 3 of the drawing likewise form a unitary structure. This latter structure is readily associated with the base I13 and Bourdon tube unitary structure by mounting and securing the base plate 32 upon the four switch mounting posts in the same manner in which the base plate 32 is secured to the mounting posts 33 and 34 as illustrated in Figure 2. The cover I8I and gasket sealing member I82 are associated with the combined structures to house and protect the Bourdon tube actuated unitary switching device.

It is obvious that the base I13 and Bourdon.

tube control unit of Figure 4 replace the base, bellows members, switching actuating lever H1 and the difierential pressure adjustment spring I28 of the switch illustrated in Figures 1 to 3. Accordingly, it will be unnecessary for an understanding of the structure and operation of this modification of my switch to illustrate and describe the remaining portions of the switch which correspond to those illustrated and described above.

The Bourdon tube is employed to directly operate the pin I 81 in the control of the auxiliary switch contacts. The pin I81 responds to movement of the Bourdon tube and is adjusted by rotating the bolt I86 with respect to the bracket I for actuating the flexible arm 82 to close the switch contacts 83 and 84 when the pressure within the Bourdon tube decreases to a selected value. This adjustment is made conjointly with a selected adjustment of the armature stop member I06. The positioning of the stop member I06 determines the length of the air gap between the armature 85 and the plate l0l when the electromagnet is deenergized and in turn controls the increase in pressure exerted between the contacts 83 and 84 upon energization of the relay and operation of the armature 85. The selective positioning of the stop member I06 likewise determines the value of the fluid pressure required to operate the Bourdon tube and pin I 81 suiiiciently to open the switch contacts 83 and 84 for deenergizing the relay. It is obvious that the circuit operates in the manner described above in connection with my differential pressure actuated switch and as illustrated in Figure 7.

The modification of my invention illustrated in Figures 5 and 6 of the drawings relates to an altitude or barometric pressure actuated waming switch. In this embodiment the portions of the unit that correspond to those illustrated and described in Figures 1 to 3 are referred to by similar reference characters.

The altitude warning switch has a base member 2 II! from which is supported a pair of threaded switch unit mounting posts and in the sectional view of Figure 5 one of the posts 2 having a nut member 2I2 threaded thereon is illustrated. Each of these mounting post members 2| I extend through the base, of which they form a part, and the inwardly extending post portions 2I3 having conical shaped ends which are employed as pivot members. An internally thread- 1 1 ed split sleeve member 2 I5 is mounted in the base 2H! and a bolt 2 l6 having a nut 2|! secured thereon is threadedly secured in the sleeve member 2 IS. A bellows 220 is mounted upon the base 2H! and the interior of this bellows is preferably temperature compensated by being evacuated to provide a relatively high vacuum and is then sealed. However, a bellows may be employed that contains air at one atmosphere of pressure when sealed. A bolt shaped plunger member 223 is secured to the bellows and a clip member 224 having downwardly projecting end portions is secured to the undersurface of the head of the plunger 223.

A cross shaped lever member 221 having upwardly extending crater portions 2'28 formed near the end of .two of the oppositely disposed arms is mounted with the crater portions supported upon the pivot posts H3 and these members cooperate to form substantially friction free bearing elements. A downwardly extending crater 230 formed in a third arm of the cross shaped lever 221 engages the downwardly extending end portions of the clip and pivot member 224 to also provide substantially friction free bearing elements. A bracket member or strap 23! is supported in a crater 232 which extends upwardly at the end of the third arm of the lever and the other end of the bracket is secured to the end of the main adjusting spring I28. Also mounted upon and extending through the base 210 is a bolt member 233. The head of the bolt has a kerf formed therein to provide for rotation of the bolt from the exterior of the casing. A segmental shaped plate member 233 is threadedly secured to the bolt 233. The outer surface of the plate is so shaped as to abut the switch casing member to prevent rotation of the plate although permitting vertical adjustment of the plate upon the bolt 233 by rotation of the threaded bolt member.

A spring 235 is mounted upon the bolt 233 and secured at one end to the plate 233. The spring 235 is secured at the other end to the fourth arm of the cross shaped lever and for this purpose the end of the spring is mounted in a groove 231 and through an opening 238 formed in the lever arm. An insulated pin 239 is secured at one end to the lever member 221 for operation thereby and the other end of the pin is connected to and actuates the auxiliary switch contact carrying resilient arm 82. In the sectional view of Figure 5 two of four mounting posts 290 are illustrated as being broken away adjacent to the'base upon which they are secured. It will be apparent that the base 2"] and the members supported thereon constitute a unit which may be secured to the sub-assembly base member 32 by connecting the mounting posts 299 to the spacing members 35, as illustrated in Figures 2 and 3, for operation of the relay and associated switching mechanism.

The casing 29l of the altitude warning switch embodiment of my invention cooperates with the gasket sealing member 292 for the protection of the switching mechanism. The casing also has a window 293 upon which is preferably mounted a pane of plastic material 294. The window pane 294 is mounted between the casing and a plate 295 which is secured to the casing. The plate 295 has an opening therein and on the plate adjacent to the pane 294 an altitude or pressure indicating scale is formed. The scale, illustrated in Figure 6, cooperates with the main spring setting as indicated by the segmental plate member I29 and this plate is adjustable 12' for determining the cut-in point of the electromagnet and switching mechanism. The scale is illustrated as indicating the pressure in inches of mercury for which the switch operation is adjusted. This scale may readily be converted to the corresponding feet of altitude at which the switch will operate, although a scale directly reading in feet of altitude is also normally formed on the plate together with other information including the voltage and current rating of the switch.

In the operation of the altitude warning switch one arm of the cross shaped lever 22! is acted upon by the main adjusting spring G28 to bias the lever for movement in a counter-clockwise direction and it will be noted that the spring 235 also biases the opposite arm of lever 221 for movement of the lever in the same direction. Accordingly, the operation of the two adjustment spring members is additive with respect to the pivoted lever 221. The end of this fourth arm of the lever extends between the head of the threaded bolt member 2l6 and the nut member 2H mounted thereon. The head of the bolt member and the nut are both threadedly adjustable and serve as stop members to limit the movement of the pivoted lever member 22].

Upon a decrease in ambient pressure accompanying an increase in altitude the bellows 220 is expanded and with the aid of the biasing springs I28 and 235 actuates the lever 22'! in the counterclockwise direction to lower the position of the switch actuating pin 24!]. The contact 89 is selectively positioned by the stop I06 in a manner that when a selected altitude is reached the arm 82 will be lowered suiiiciently to close the auxiliary switch contacts 83 and 84 to energize the electromagnetic structure 66 and operate the main switch contacts. The electromagnet also operates to attract armature 85 to raise the position of switch contact 93 for increasing the pressure between switch contacts 83 and 93 and for assuring operation of the switch until the altitude decreases to a selected lower value.

The main switch contacts are employed to operate the load in a circuit of the type illustrated in Figure 7 and described above and which may actuate a siren or a series of signals for warning the person or persons in the aircraft to employ oxygen supply equipment.

The several modifications of the switching unit ,of my invention each employ an electromagnet and associated switching mechanism mounted upon the sub-assembly plate 32. "This mechanism may be interchangeably employed with the various types of switch actuating means in the manner illustrated and described for readily adapting the switch unit to be variously employed in addition to providing for the ready maintenance and replacement of parts for a particular unit.

In accordance with my invention the main switch contacts are of relatively large size and are rapidly actuated by the electromagnet member to thus provide a switching unit that may be safely employed with circuits of large power and high inductive capacity.

It will be readily apparent that in accordance with my invention many changes may be made in the details of construction and arrangement of the parts. For example, the auxiliary switch contact members may, if desired, be supported and arranged for operation of the electromagnet upon an increase in the difl'erential pressure of the fluids, or upon an increase in fluid pressure. The

invention may also readily be adapted for control by temperature and other condition responsive means in addition to pressure and is correspondingly subject to a variety of modifications and uses. The scope of the invention is accordingly defined by the appended claims.

I claim as my invention:

1. A switch comprising, an electromagnet, first armature means magnetically operated by said electromagnet, switch means for controlling the operation. of the electromagnet, said switch means including a first switch contact supported and biased for movement in one manner and a second switch contact supported for operation by a second armature means to assume a first position when the electromagnet is deenergized and a second position when the second armature means is actuated by energization of the electromagnet, means for adjustably determining the distance through which the second armature means is actuated by the electromagnet to. vary the distance between the first and second positions of said second contact, and'means responsively actuating the said first switch contact to control the operation of the switch.

2. A switch comprising, an electromagnet, first armature means magnetically operated bysaid electromagnet, switch means for controlling the operation of the electromagnet, said switch means including a first switch contact supported and biased for movement in one manner and a second switch contact supported for operation by a second armature means to assume a first position when the electromagnet is deenergized and a second position when the second armature means is actuated by energization of the electromagnet, means for adjustably determining the distance through which the second armature means is actuated by the electromagnet to vary the distance between the first and second positions of the said second contact, means including a pivoted and biased lever movable for actuating the said first switch contact to control the operation of the switch and said electromagnet, means for selectively adjusting the bias of said pivoted lever, and difierential fluid condition responsive means for operating said pivoted lever to control the operation of the electromagnet.

3. A unitary condition responsive control device comprising, means energized by closing of the switching means, condition responsive means for controlling the operation of the switching means, armature means operated by the magnetic means also controlling the operation of the switching means, means for adjusting the operative relationship between the condition responsive means and the switching means to vary the value of the condition at which the switch is actuated in a first manner, and means for afl'ecting the operation of the magnetically actuated armature means to vary the value of the condition at which the switch is actuated in a second manner.

4. A control device, comprising, an electromagnet, a first armature controlled by said electromagnet, a second armature controllable by said electromagnet and having a first switch contact mounted thereon, a second switch contact cooperable with said first switch contact, an electrical connection between one of said contacts and said electromagnet, actuation of said second armature by said electromagnet moving said first contact toward said second contact, said second switch contact being biased to a first position, and means operable to position said biased switch contact switching means, magnetic 14 into and out of engagement with said first switch contact to control the energization of said electromagnet.

5. A control device, comprising, an electromagnet, a first armature controlled by said electromagnet, a second armature controllable by said electromagnet and having a first switch contact mounted thereon, a biased second switchcontact cooperable with said first switch contact, an electrical connection between one of said contacts and said electromagnet, actuation of said second armature by said electromagnet moving said first contact toward said second contact, means operable to position said biased switch contact into and out of engagement with said first switch contact to control the energization of said electromagnet, and means associated with said electromagnet to conduct magnetic flux in such a manner as to attract and hold said second armature.

6. A control device, comprising, an electromagnet, a first armature controlled by said electromagnet, a second armature controllable by said electromagnet and having a first switch contact mounted thereon, a second switch contact cooperable with said first switch contact, an electrical connection between one of said contacts and said electromagnet, actuation of said second armature by said electromagnet moving said first contact toward said second contact, said second switch contact being biased to a first position, an adjustable pivoted lever operable to move said switch contacts into and out of engagement with each other to control the energization of said electromagnet, and condition responsive means operable upon a change of condition to actuate said lever.

7. A control device, comprising, an electromagnet, a first means magnetically actuated by said electromagnet, an armature magnetically controlled by said electromagnet and having a first switch contact mounted thereon, a second switch contact cooperable with said first switch contact, an electrical connection between one of said contacts and said electromagnet, actuation of said second armature by said electromagnet moving said first contact toward said second contact, said second switch contact being biased to a first position, a pivoted lever operable to move said switch contacts into and out of engagement with each other to control the energization of said electromagnet, condition responsive means operable upon a change in condition to actuate said lever, and adjustable biasing means cooperable with said lever to variably adjust the condition value at which said condition responsive means will actuate said lever.

8. A control device, comprising, an electromagnet, a first armature means controlled by said electromagnet, a second armature controllable by said electromagnet having associated therewith switching means, an electrical connection between one of said contacts and said electromagnet, actuation of said second-armature by said electromagnet moving said first contact toward said second contact, said switching means being normally biased to one of its positions, means associated with said electromagnet when said electromagnet is energized for conducting magnetic flux from said electromagnet to attract and hold said second armature, and means responsive to one variation in pressure for moving said switching means against its bias to a position whereby said electromagnet is deenergized.

9. In a control device, switching means movable between open and closed circuit positions,

condition responsive means for actuating said switching means mechanically to closed circuit position at a first value of the condition, an electromagnet, electrical connections between said switching means and said electromagnet, energization of said electromagnet being controlled by said switching means, first and second armatures actuated by said electromagnet, means controlled by said first armature, said second armature being operatively connected to said switching means to shift said switching means mechanically and thereby shift the position to which said condition responsive means must actuate said switching means to open the circuit therethrough, whereby the switching means is actuated to circuit open position at a second value of the condition.

10. In a control device, switching means movable between open and closed circuit positions, condition responsive means for actuating said switching means mechanically to closed circuit position at a first value of the condition, an electromagnet, electrical connections between said switching means and said electromagnet, energization of said electromagnet being controlled by said switching means, first and second armatures actuated by said electromagnet, means controlled by said first armature, said second armature being operatively connected to said switching means to shift said switching means mechanically and thereby shift the position to which said condition responsive means must actuate said switching means to open the circuit therethrough,

whereby the switching means is actuated to circuit open position at a second value of the condition and means for adjusting the extent to which said switching means is shifted by said second armature. I

11. In a control device, means defining a sealed chamber having a fiexible wall, a pair of pressure responsive means within said chamber, a pivoted lever, connecting means between each of said pressure responsive means and said lever, said lever being positioned by the difference in force produced by said pressure responsive means, and an electric switch actuated by said lever, said 16 switch being located outside said sealed chamber.

12. In a control device, means defining two expansible chambers, means defining a sealed chamber enclosing said first named chamber defining means and having a flexible wall, a pivoted lever, connecting means between said first named chamber defining means and said lever, said connecting means extending through said flexible wall whereby said lever is positioned mechanically through said flexible wall, and an electric switch actuated by said lever.

13. In a control device, a pair of bellows within an enclosure, a diaphragm sealing one side of the enclosure, a lever, means extending through said diaphragm from each bellows and engaging said lever, and a switch operatively connected to said ever.

ALBERT E. BAAK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 365,438 Jacobs June 28, 1887 510,003 Delany Dec. 5, 1893 1,063,369 McElroy June 3, 1913 1,542,931 Foote June 23, 1925 1,636,900 Darker July 26, 1927 1,708,265 Freeman Apr. 9, 1929 1,780,676 Hough Nov. 4, 1930 1,880,859 Davis Oct. 4, 1932 1,904,326 Penn Apr. 18, 1933 1,942,913 Beggs Jan. 9, 1934 1,951,245 Jardine Mar. 13, 1934 2,061,270 Carlson Nov. 17, 1936 2,087,216 Betz July 13, 1937 2,177,480 Gaynor Oct. 24, 1939 2,179,599 Raney Nov. 14, 1939 2,255,496 Wyman sept. 9, 1941 2,275,866 Runaldue Mar. 10, 1942 2,283,175 Berger May 19, 1942 2,360,723 Schaefer Oct. 17, 1944 

